Transfer RNA is the smallest polymeric form of RNA. In abundance, the tRNA comes next to rRNA and amounts to about 15% of total RNA of the cell. The tRNA molecule serves a number of functions; the most important of which is to act as specific carriers of activated amino acids to specific sites on the protein-synthesising templates. As the function of tRNA is to bind the specific amino acids, there must be at least one for each amino acid. There are, thus, at least twenty tRNA molecules in every cell. Since the code is degenerate (i.e. there is more than one codon for an amino acid), there may also be more than one tRNA for a specific amino acid.